Conventional municipal water treatment (MWT) includes multi-stage filtration and sequential process steps for coagulation, flocculation, and sedimentation. Typically, a minimum of two stages of filtration must include coarse 2-3 mm mesh filters at the inlet and 20-40 μm multi-media filters for finishing although many utilities have more intermediate filtration steps. The hydraulic retention time (fluid residence time) in the combined coagulation-flocculation-sedimentation process can be 5-10 hours long, depending on the quality of the source water.
With reference now to FIG. 1, a conventional water treatment facility is illustrated. This, of course, is merely an exemplary system. As shown, a system 10 includes a source 12 of any of a variety of types of fluid such as surface water, ground water, waste water, brackish water, seawater . . . etc. This water is fed to a screen filter 14—which is typically operative to filter out particles in the 1 mm to 3 mm range. After these relatively large particles are removed, a pH adjustment is made to the water and potassium permanganate (KMnO4) is added to the supply in a carbon reactor/mixer 16. This chemical is typically added for taste and odor control. Other substitutes may include ozone and other oxidizing agents. Next, chlorine is added to the supply and mixed in a mixer 18. Flash mixing wherein coagulants (e.g., Alum, FeCl3, ACH, etc.) are added is then performed in a flash mixer 20. Flocculants—made of long chain polymers with a high molecular weight—are added at a flocculation stage and mixed in a slow mixer 22. The supply is then sent to a sedimentation tank 22 where particles settle out of the effluent as a result of gravitational forces. The flow from the sedimentation tank is then provided to a multimedia filter 26 which operates to remove remaining small particles. The output of the system can then be used for a variety of purposes. In one form, chlorine is added to the output. The multimedia filter is frequently backwashed, and the backwash is optionally fed back to the water source. In this backwash, or feedback, path, a dewatering stage 28 may be provided whereby water is provided back to the source and sludge is removed.
As noted above, the water purification process described requires a substantial amount of time. With reference now to FIG. 2, it is seen from an example flow 50 that the basic steps include rapid mix (including coagulation), flocculation, sedimentation, and filtration. As shown, the rapid mix stage 52 takes 30 seconds to 2 minutes to complete. The flocculation stage 54 requires 20 to 45 minutes of processing time. Sedimentation 56, or any other alternative solid removal process, typically requires at least 1 to 4 hours (and possibly up to 10 hours) of processing. Last, filtration 58 also requires a definitive amount of time. The extended time periods are not only a problem for municipal-type purification systems but also water purification systems that are used in other environments, such as a lab environment.
Therefore, it would be desirable to have available an alternative water treatment system that can more efficiently and effectively purify water.